1. Field of the Invention
The present invention relates to a cathode ray tube comprising a plurality of electron guns and an image correcting method in the cathode ray tube.
2. Description of the Related Art
In an image display apparatus such as a television receiver or a monitor apparatus for computers, cathode ray tubes (CRT) are widely used. A cathode ray tube forms a scan screen according to scanning of an electron beam by irradiating an electron beam toward a phosphor surface from an electron gun provided inside the cathode ray tube. A cathode ray tube comprising a single electron gun is common. However, in recent years, a cathode ray tube with multiple electron guns has been developed. In this type of cathode ray tube, a plurality of divided screens is formed by a plurality of electron beams-irradiated from a plurality of electron guns, and image display is performed through forming a single screen by joining the plurality of divided screens. The techniques regarding the cathode ray tube comprising the plurality of electron guns are disclosed in, for example, Japanese Patent Application laid-open No. Sho 39-25641, Japanese Patent Application laid-open No. Sho 42-4928 and Japanese Patent Application laid-open No. Sho 50-17167. The cathode ray tube comprising the plurality of electron guns has advantages such as that the depth can be shortened while the screen is enlarged.
In the above-mentioned cathode ray tube with multiple electron guns, it is preferable that the joint area of the divided screens are as inconspicuous as possible when joining the plurality of divided screens to display an image as a single screen. However, in the related art, the technique for making the joint area of the divided screens inconspicuous is insufficient so that a fine image cannot necessarily be obtained on a whole screen. For example, in a cathode ray tube, influence of geomagnetism or the like differs depending on the environment in which the tube is used. Therefore, image distortion or the like occurs and display in the above-mentioned joint area is adversely influenced. With the cathode ray tube with multiple electron guns of the related art, the display control of the joint area is environment dependent and therefore insufficient. Moreover, in a cathode ray tube, image display performance deteriorates through a processing circuit such as a deflection circuit being changed over time. In this respect, with the cathode ray tube with multiple electron guns of the related art, display control of the joint area is also dependent on the changes over time and thus is insufficient. As described, in the related art, the technique for appropriately joining the plurality of divided screens by the display control considering the environment, the changes over time or the like is insufficient. Therefore, it is difficult that the joint area on the screen are always inconspicuous so as not to disturb watching.
The invention has been designed to overcome the foregoing problems. The object is to provide a cathode ray tube and an image correcting method which can join a plurality of divided screens with the joint area being inconspicuous, and perform fine image display.